The current invention generally relates to a generator control unit (GCU), and more particularly, to a generator control unit (GCU) that is capable of tolerating a ground fault in the generator, be that in the permanent magnet generator (PMG) wiring or field wiring This generator control unit (GCU) can tolerate a ground fault that commonly results from the incidental contact of the permanent magnet generator (PMG) wire or a field coil wire with the chassis of the generator.
It is generally known that power generators require a generator control unit (GCU) to control their output. In order to control the generator output, the field current is adjusted to compensate for the load and speed variations. The field current is commonly derived from a permanent magnet generator (PMG), which is incorporated into the generator itself.
A common problem that occurs in these generator control unit (GCU) is a ground shortage that occurs when the electrical wires touch the chassis as a result of insulation breakdown. This ground shortage is undesirable as such shortage causes the system to stop operation completely at the same time potentially damaging expensive electrical components within the generator control unit (GCU).
Typically, the ground shortage issues can occur in permanent magnet generator (PMG) wire or in a field coil wire. Although deriving from two separate components, the shortage caused when either of these wires touches the chassis could be significantly detrimental to the continuous operation of an aircraft power generation system by damaging its generator and its generator control unit (GCU).
FIG. 1 shows a prior art embodiment wherein the electrical components are connected directly to the ground referenced control domain, hence making it difficult to tolerate an electrical shortage to the chassis.
FIG. 1 shows a direct connection from inverted buck regulator 106 to ground referenced control domain 112. During a ground fault when a metal wire touches the chassis at a second location other than the intended ground connection 111, a short circuit will occur, creating an undesirable over-current. The sudden spike in current could be detrimental to the operation of the generator control unit (GCU), often causing the entire system to shut down.
As it can be seen from FIG. 1, the traditional prior art generator control unit (GCU) is not set up to withstand the ground fault caused when a permanent magnet generator (PMG) 100 wire or a field coil 108 wire come in touch with the chassis.
In order to address the ground shortage issues deriving from the permanent magnet generator (PMG) wire shorting with the chassis, the current art sometimes attaches a heavy, bulky, and burdensome component called a permanent magnet generator transformer (PMG transformer) to isolate the input. These permanent magnet generator transformers (PMG transformers) have to be rated for the full power of the permanent magnet generators (PMG) that they are attached to making them expensive in addition to being heavy, bulky, and burdensome.
In order to address the ground shortage issues deriving from the field coil wire shorting with the chassis, the current art lacks a suitable solution other than to add an additional isolator that can withstand the sudden spike in voltage. Consequently, without the additional isolator, the entire controlled frequency generator (CFG) will stop and shut down when the field coil wire touches the chassis.
Hence, it can be seen that there is a need for an innovative system and method for providing continuous operation of a generator control unit (GCU) in the event of a ground short to the chassis from either a permanent magnet generator (PMG) wire or from a field coil wire without the need of heavy and burdensome isolators that are unnecessarily expensive. Moreover, there is also a need for an innovative system and method to be able to detect such a ground short to the chassis despite the continuous operation for future maintenance.